/Engine/Source/Runtime/Engine/Classes/Animation/AttributesContainer.h
Adds, if not yet existing, a new attribute type/value entry of the specified AttributeType.
The ptr to the added/existing entry, to be used for populating the data, nullptr if adding it failed
template<typename AttributeType> AttributeType * FindOrAdd ( const [FAttributeId](API\Runtime\Engine\Animation\FAttributeId) & InAttributeId )